The present invention relates generally to induction heating and in particular to an induction heating apparatus of the type having a pair of inversely parallel connected thyristors wherein a transformer is employed for simultaneous application of gating control pulses to the thyristors.
In induction heating systems wherein a pair of inversely parallel connected thyristors is employed as a switching element, the thyristors are gated alternately into conduction to convert low frequency energy into high frequency energy. Although the use of a pair of thyristors is advantageous in terms of economy over induction heating systems in which a thyristor and a feedback diode are employed as a switching element in combination with a heavy duty fullwave rectifier, the prior art control circuit is provided with a sequence control function to enable the thyristors to be alternately fired in succession depending upon the polarity of the input power source. However, such sequence control adds complexity to the system with a resultant increase in cost. Furthermore, to ensure safe gating operation, it is advantageous to quickly turn off a conducting thyristor as soon as the other thyristor is driven into conduction by application of a negative bias to the control gate of the thyristors. The aforesaid functions have been realized at the expense of increased costs which have impeded the widespread use of induction heating systems for household applications.